US2798909A - Mechanical rectifier contacts - Google Patents

Description

July 9, 1957 o. JENSEN MECHANICAL RECTIFIER CONTACTS 6 Shee ts-Sheet 1 Filed Aug. 29, 1952 IN VEN TOR. 017a JE/VJ'E/V July 9, 1957 Q JENSEN 2,798,909

MECHANICAL RECTIFIER CONTACTS Filed Aug. 29, 1952 6 Sheefis-Sheet 2 IN VEN TOR. flrra Java-Ar MM BM {11 imp/W July 9, 1957 o. JENSEN MECHANICAL RECTIFIER CONTACTS 6 Sheets-Sheet 3 Filed Aug. 29, 1952 IN V EN TOR. 0pm Aw-r July 9, 1957 JENSEN 2,798,909

MECHANICAL RECTIFIER CONTACTS Filed Aug. 29, 1952 6 Sheets-Sheet 4 i M if aim 2 as IN VEN TOR. drra JEMs/V July 9, 1957 o. JENSEN MECHANICAL RECTIFIER CONTACTS 6 Sheets-Sheet 5 Filed Aug. 29, 1952 NTOR. ENS! oar 5 I J-rrmF/VEKS July 9, 1957 Q JENSEN 2,798,909

MECHANICAL RECTIFIER CONTACTS IN V EN TOR. firra Jaw/sew Unite MECHANICAL RECTlFlER CONTACTS" My invention relates to mechanical converters and r'ectifie'rs', of the type set forth in Patent No. 2,693,569 issued November 2, 1954, and is more particularly directed to 'a"novel'contact assembly which is readily adjustable to prevent bouncing and insure uniform contact engagement and has the further advantage of being readily removable'and replaceable.

A'meclianical rectifier produces direct current by makin'gbridging contact between a proper phase of an A. C. system and the associated D. C. system during the time intervalthe particular phase of the A. C. system is capable of delivering energy in the desired direction and breaking the bridgingcontact when the A. C. phase reverses its voltage" in relationship to the D. C. voltage. This operation is performed sequentially and repeatedly in synchronism with the A. C. frequency.

Mechanical rectifiers utilize a commutating reactor, which is a non-linear or saturable type reactor, to step the current when it passes through zero value. This operation is fully described in the above mentioned Patent No. 2,693,569 issued November 2, 1954. During some period of each'stepping operation either contact engage ment or disengagement must be completed. Hence, in a three phase mechanical conversion unit it is necessary for the contact assembly to make and break the circuit 196,000 times per hour. It is therefore apparent that contact assembly is a vital component of the conversion unit and must be designed to contribute directly to the quality of conversion performance. Copending application Serial No. 307,024, filed'August 29, 1952, is directed to the contact time adjustment for the contact assembly and this application is directed to'the contact assembly per se.

The make and break of the contact assembly isdesigned tooccur during the stepping length of the current so that contact engagement and disengagement will occur during zero current flow. However, even though there usually is an absenc'e'of current at the time of making and breaking connections the contact assembly must carry 5,000 amperes and serve through 1,866,000,000 operations for a 360-day period. Improper contact time adjustmentfor a short period'of time may result in contact pitting, burning and corrosion.

Hence, in order not to further impair proper operation of the converter it is desirable to provide removable and replaceable contact assembly means whereby rapid and easy interchange of movable and stationary contacts is possible. 7

Accordingly, one object of my invention is to provide a composite compact contact assembly unit which is easily and rapidly removable and replaceable.

Another object ofmy invention is to provide a mechanical converter whichlends itself to the interchange of contact assemblies.

A still further object of my invention is toprovide a simple contact assembly unit which contains both the stationary and movable contacts and can be rapidly removed from the converter apparatus.

rates Pat '1 ice Another object'of my invention is to provide a contact assembly which is not connected to the push rod'assembly or contact actuating arm and hence is rapidly and'ea'sily removed Without interfering with the push rod'assembly or adjustment thereof.

Another object of my invention is to provide new and novel contact assembly which is simple in design and easily repaired;

In prior art contact assemblies for mechanical con verters, considerable bouncing and misalignment of the contact occurred.

However, it is imperative that moving contacts seat themselves against the stationary contacts without any biasing action, since in the event of contact biasing, metallic'contact would be made and broken several times during each engagement operation to thereby cause aseries of arcsto appear, which would cause eventual destruction of the contacts.

, However, with proper alignment of the mating contact surfaces, so that the moving contact does not rock when contact is made, bouncing is eliminated. In the contact assembly of my invention a contact adjusting bushingis provided with a'plurality of jack screws which are accessible when the protective hood is removed. With the aid of four D. C. circuits, arranged circumferentially around the movable contact, the jack screws are adjusted until proper alignment of the mating surfaces between the stationa'ry and movable contact is accomplished;

Accordingly, a further object of my invention is'to provide a contact assembly for a mechanical converter which is rapidly and easily adjusted to obtainproper alignment of the mating contact surfaces. I

Another object of my invention is to provide a contact assembly whereby a simple and novel structural arrangement permits proper adjustment to eliminate bouncing.

A still further object of my invention is to provide a novel contact assembly which will on seating not bounce or oscillate.

A still further object of my invention is to provide a' novel adjustment means for a contact assembly which will insure'proper alignment between the stationary'contacts and the bridging movable contact.

These and other objects of myinvention will be apparent from the following description When taken in connection with the figures in which:

Figure l is a schematic electrical connection diagram of a single mechanical rectifier unit in which my invention is used.

Figure 2 is a perspective view of the control of the push rod and its effect on the contact engagement and disengagement.

Figure 3 'is an exploded perspective view showing the contact time adjustment means.

Figure 4 is an exploded perspective view of the replaceable contact assembly.

Figure 5 is a cross-section view of the assembled replaceable contact assembly of Figure 4.

Figure 6 is a side detailed view of the push rod and associated removable and replaceable contact assembly.

Figure 7 is a top view of Figure 6 illustrating the arrangement and assembly of the removable and replaceable contact assemblies.

Figure 8 is a cross-sectional view of the contact assembly of my invent-ion, similar to Figure 5, showing the position of the contact or surfaces when they are misaligned.

Figure 9 is a view taken along the line 9-9 of- Figure 5' showing the connection and position of the D. C. circuit contactors used to adjust the alignment of the mating contact surfaces.

In Figure 1, the source of alternating current istaken. firom the alternating current lines 10 through the circuit breaker 11 to step down transformer 12. The source current is then passed through the commutating reactors 13 to step the current for switching purposes as set forth in Patent No. 2,693,569 issued November 2, 1954. The enclosure means 12 and construction of the commutating reactor 13 are more fully described in copending application Ser. No. 301,880, filed July 31, 1952, now Patent No. 2,759,128, August 14, 1956.

The current then passes through disconnect switches 14 to the contact converter 15 which forms the subject of the instant application. The contact converter 15 sequentially and repeatedly in synchronism with the A. C. frequency connects the alternating current source buses 1011, b, c to the D. C. load buses 20-21.

The contact converter 15 is bridge connected to permit better use of the power transformer 12 by doubling the phase operation of the connecter and thereby result in smoother D. C. current and less interference with commutation facilities as best seen in Figures 2, 6 and 7.

The bridge connected contact converter 15 has two sets of contacts, a negative set 25-30-27 (a-) and a positive set 26-31-28 (a+). The two sets of contacts are off set 180 electrical degrees from each other and the contacts in either positive or negative set for all the phases a, b and c are set 120 apart. The circuit may be supplied with three phase voltage a, b, c and at one period of time the load current will flow from phase a through contact a+ through the load and back over a contact cto 0. During positive commutation between phases a and b, the load current divides between these two phases by closed contacts a-l and b|-.

For the purpose of simplification, I have shown in Figure 2 the switching structure which is used at phase a, it being understood that the switch apparatus for phases b and c are identical in construction, as seen in Figure 7.

An excited type synchronous motor 40 is energized from the three phase source voltage a, b, c and drives shaft 41. A cam 42 is integrally attached to the shaft 41 and therefore driven by the motor 40. The cam 42 drives an eccentric 43. The eccentric member 43 is pinned to bell cranks 50-51 by means of pin 52. Since the bell cranks 50-51 are rotatably mounted by bearing 54' on a fixed overlap control shaft 54, the movement imparted to eccentric 43 by cam 42 is a reciprocating motion which in turn is imparted to the bell cranks 50-51.

The cross extension arms of the bell cranks 50-51 are connected by rocker arm pins 60-61 which serve as the driving means for push rods 62 and 63. The rocker arm pins 60-61 are connected to extending arms 50-51 by means of bearing 60-61 so that these pins 60-61 have a rotational movement to enable them to maintain constant engagement with the push rods 62 and 63 as will hereinafter be more fully described.

Push rods 62 and 63 are identical in construction and are shown in the exploded detailed view of Figure 3 and in the detailed side view of Figure 6. Upward movement of push rod 62 imparted thereto by the rocker arm pin 60 will urge the moveable disc shaped bridging contact 31 against the bias of contact spring 81 and thereby disengage it from engagement with stationary A. C. contact 28 and stationary D. C. contact 26.

The structure and operation of the adjustable push rod 62 will best be understood from the following description taken in connection with the exploded detailed view of Figure 3 and detailed side view of Figure 6. The push rod 100 is provided with external splines 101 at its lower portion and an insulated head 102 at its upper portion. The reduced cross-sectional head 103 and the enlarged cross-sectional portion 104 of insulating head 102 are sufiiciently small to move through the opening provided by the space between stationary contacts 26-28 to thereby enable the head 103 to engage the bridging contact ring 31. Hence, when the contact rod 100 is moved upward by the rocker arm pin 60 or 61 the reduced cross-sectional portion 103 of the insulating head 102 tionary contacts 25-27 or 26-28 and portions 103 will engage the lower surface of the ring contact 30 or 31 and urge it upward against the bias of contact spring or 81 to contact disengaged position.

The insulating material 102 is designed to prevent the movable contact 30 or 31 from moving away from the stationary contacts with an oscillatory motion to thereby prevent delayed contact separation which would decrease the safety portion of the step.

External splines 101 located at the lower edge of the contact rod mesh with the internal splines 105 of the worm gear 106. Hence, the push rod 100 has vertical movement with respect to the worm gear 106 but is restricted from having rotational movement with respect thereto due to the mesh of splines 101 and 105. The worm gear 106 as will hereinafter be more fully explained has no vertical movement and is restricted to rotational movement. The worm gear 106 is in mesh with the worm 108 which is controlled by the shaft 109 as seen in Figures 2 and 3. Hence, manual rotation of shaft 109 will rotate worm 108. The mesh engagement between worm 108 and worm gear 106 will cause worm 109 to rotate the worm gear 106. The mesh engagement of the internal splines 105 of worm gear 106 with the external splines 101 of push rod 100 will cause rota tional movement of the push rod 100 due to the rota tional movement of worm gear 106. As will hereinafter be more fully explained, rotational movement of push rod 100 will cause the adjusting screw 110 to thread toward or away from the push rod 100. Thus, rotation of the worm 108 will cause a change in the over-all length of the push rod 62.

The lower portion of push rod 100 is hollow and has a threaded internal portion 111. The internal threads 111 mesh with the external threads of the adjusting screw 110. Near the lower portion of the adjusting screw 110 is a flange 112 which acts as a stop or rest for the return spring cap 113. The return spring 116 is concentric with the adjusting screw 110 and is seated at its lower end against the return spring cap 113 and at its upper end against the stationary ledge 107. The lower end of the adjusting screw 110 is provided with a slot 117 that registers with the key or projection 118 on rocker arm pin 60.

The engagement of projection 118 with slot 117 prevents rotational movement of the adjusting screw 110 so that its motion is limited to vertical movement. Thus, during operation of the rectifier the synchronous motor 40 oscillates the pin 60 through eccentric 43 and bell cranks 50-51 and causes the push rod 100 and attached adjusting screw 110 to move as a single unit.

As heretofore noted the rocker pins 60-61 are mounted in bearing 60' and 61 of extension arms 50 and 51. The,

projection slot engagement 117-118 between the push rod 62 and rocker pin arm 61 are always in engagement due to the force of return spring 116 and the rotational movement of the pins 61 permitted by the bearing 61' as seen in Figure 6.

A detailed view of the support mounting and construction of the push rod of Figure 3 is shown in Figure 6.

A housing serves as a guide and vertical support for the push rod 100. Anti-friction bearing 126-127 on the push rod 100 serve as the physical support and guide for the vertical movement of the push rod means 62. The push rod 62 is force fed lubricated by means of oil which is fed into the area between the rod 100 and the housing 125 through port 128 from oil chamber 129. A plurality of oil drip shields 130, 131, 132 are attached to the upper portion of the push rod 100. The oil drip shield 130, 131, 132 function in a well known manner to prevent excess oil from reaching the insulating head 103 and thereby prevent any oil from reaching the bridging electrical contact 30. Return holes 135 are provided to return the excess oil through the hollow interior of the push rod 100. l

The entire push rod assembly 62 of removable contact assembly 71 and housing means 125 are supported by stationary structures 141 and 142. The lower stationary structure 141 has an extension member 107 which serves as a bearing support for the worm gear 106 and also as the upper seat for the return spring 116. The extension 145 of stationary support structure 141 serves as the support for the housing member 125. The flange 148 on the housing 125 abuts the stop bushing 149 of support 145. The flange 148 also serves as the upper abutment for the worm gear spring 150, the lower end of this spring resting on the worm gear 106 to'continuously urge the gear 106 into engagement with the bushing 107.

Thus, the operation of push rod assembly 62 and 63 is as follows: rotation of the synchronous motor 40 oscillates the bell crank member 50-51 about the fixed axis 54'; The sliding engagement between slot and pin 117- I l8 of the push rod and rocker arm pin-60 or 61 plus the guide of housing 125 imparts onlyvertical movement to the push rod 100. Since the push rod assemblies 62 and 63" are mounted on opposite ends of the bell crank 50-51, they will be 180 out of phase with each other. At a predetermined position of the upstroke the insulating head 103 will engage the bridging contact 30 and move it upward'against the downward bias of the 150 pound contact spring 80 and thereby interrupt the circuit between phase bus 10a at stationary contact 27 and the D. C. negative bus 20 at contact 25. The-bridging contact 30 will remain disengaged from these stationary contacts 25-27 during the' remaining portion of the upstroke and for a predetermined time or distance of the down stroke travel'of'the push rod assembly 62.

It will therefore be apparent that for a given R. P. M. of the synchronous motor 40 the time of contact engagement and disengagement and length of time that the contactsremain engaged and disengaged will be a function of the elfective length of the push rod assembly 62-63.

As heretofore noted adjustment to modify the length of the individual push rod assemblies 62'and 63 for phases a, b and c is accomplished by means of worm 108 and worm gear 106. The worm gear 106 is continuously urged against the bushing 107 by means of hold-down spring 150 and hence has no vertical motion either independently or with the push rod 100.

Thus, when the rectifier is operating, the spline mesh 105-111 between the worm gear 106 and push rod 100 permits the rocker ann pin 61 to oscillate the push rod assembly 62in a vertical path while the worm gear 106 remains stationary. Hence, while the machine is running andunder load, the Worm gear 106 and 108 will remain stationary and thereby be available for adjustment to modify the effective length of the push rod 62. Rotation of the worm gear 106 by the operators rotation of worm 108-109 will cause the push rod 100 to rotate due to mesh therebetween at splines 105-109. However, since the adjustment screw 110 is keyed to the rocker arm 60 or 61 and held in tight engagement therewith by means of return spring 116, the adjustment screw 110 will not be rotated by the rotation of worm gear 106. Hence, the push rod 100 will be threaded toward or away from the adjustment screw 100, depending on the direction of rotation of the worm 108, to thereby alter the effective length of push rod assembly 62.

As best seen in Figure 7, six contacts may be used in a unit to rectify 5,000 amperes. That is, a pair of contact assemblies and push rod assemblies are provided for each phase a, b, c of the source to alternately connect it to the positive and negative buses 20-21 of the load. Thus, each unit switching each phase either to positive or negative can be independently and individually adjusted to modify the length of the push rod and achieve proper contact time adjustment.

As fully set forth in copending application Serial No. 212,017 filed February 21, 1951 the mechanical converter will operate at its greatest efficiency when the contact converter 15 causes contact engagement and disengagement at 'the proper time during the current stepping operation caused by the commutating'reactor 13. Hence, with the apparatus of my invention the push rod assembly 62 can be modifiedin length to-adjust for contact time engagement and disengagement and length of time of contact engagement and disengagement to insure maximum efficiency of operation.

However, the adjustment or modification of the effective length of push rod assembly 62 is merely limited to altering the time and length of time of contact engagement and disengagement and will not eliminate possible misalignment and resulting'bouncing of the movable contact 31 when it is returned to contact engaged position. With the contact assembly-of my present invention adjustment means are provided to -obtain proper mating contact alignment andthereby prevent'bouncing. The contact assembly unit 70'is best seen-in Figures 2, 4, 5, 6, 7 and 8.

The 150 pound contactcompression spring 81 has a disc member 121 attached to one end thereof and the bridging contact member 31 attached at the other end thereof. The disc 121 has three grooves 122 drilled in the upper surface thereof to receive the lower ends of jack screws 1-23. The jack screws 123 are held in the contact adjustment bushing which has a cylindrical extension 124. The cylindrical extension 124 fits into opening 125' of the contact block or phenolic housing 126'. The entire contact unit is housed and protected by the phenolic contact block 126. The phenolic housing 126 is provided with a channel 138 on each of its four sides to increase the creepage distance and permit access for the governing- D. C. circuit as will hereinafter be more fully described; Openings 128 are provided in top of housing 126 to receive screws 129 (see Figure 6) which are threaded into the holes 130 of the pure silver stationary'contacts 26-28 to secure them to the housing 126.

Openings in the top ofphenolic contact block 126 receive andpermif easy access to the jack screws 123. Hence, compression spring 81 urges the movable brid ing contact 31 against the stationary contacts 26-23 which are securedt'o thehousing 126 by means of screws 128 andu'rges the contact adjustment bushing 120 against the upper portion of the housing 126 by force transmitted'through disc 121 and jack screws 123.

All the current carrying members 26-28-31 are made of pure silver thereby providing a constant and extremely small voltage drop. The loss in each contact assembly of a 10,000 ampere machine is of the order 200 watts. This slight loss is an important factor in the overall high efficiencyof' the mechanical converter and also has the additional advantage of requiring a low capacity cooling system.

The movable bridging contact 31 for a 5,000 ampere converter is 1 /8 inches in diameter and the stationary contacts 28 (a) and 26 are one inch wide and two inches long. Lightness of the moving members offers little inertia for rapid action in closing and opening. The small size concentrates the force of the compression spring to aid in firm seating of the bridging contact 31 over the entire seating area of the stationary contacts 26-28.

The use of a large compression spring 81 plus the concentration of forces permits the use of small contacts.

Adjustment'ofthc alignment of the mating contact surfaces is accomplished by means of jack screws 123 and governed by the signal D. C. circuit shown in Figures 8 and 9. When the contact surfaces are misaligned, as best seen in Figure 8, the bridging movable contact 31 will come into make position at an angle (dotted lines) with respect to the stationary contacts and hence will rock and bounce. The jack screw arrangement 123 and the signal D. C. circuits utilized to obtain proper contact alignment will now be "described,

The electrical prongs 151, 152, 153 and 154 and their associated electrical connections 155, 156, 157, 158 respectively are clamped in each of the contact block 126 leakage channels 138 by means of clamp members 160 as best seen in Figure 9. The electrical prongs 151, 152, 153, 154 are spaced from the stationary contacts 28 (a) and 26 as seen in Figure 8 and are positioned circumferentially around the bridging movable contact 31. The electrical prongs 151, 152, 153, 154 are positioned circumferentially around the stationary contact 31 in proper position so that none of the prongs engage the contact 31 when it is in proper alignment with the stationary contact 26-28 as best seen in Figure 9. The four D. C. circuits 155, 156, 157, 158 have identical cir cuit. Each is provided with a series battery 161, 162, 163, 164 and series connected lamps 165, 166, 167, 168 as best seen in Figures 8 and 9. The D. C. circuits are connected at one end to the electrical feelers or prongs 151, 152, 153, 154 and at the other end 181, 182, 183, 184 are connected to terminal connector box 170.

All the terminals 181, 182, 183, 184 are connected to the terminal 185 to which lead 171 is connected. The lead 171 is electrically connected to the cylindrical extension 124 of the contact adjustment bushing 120 in any suitable manner.

When the bridging contact 31 is misaligned with the stationary contacts 26-28 as shown in Figure 8, it will engage the feeler 153 of D. C. circuit 157 but will move further away from feeler 151 of D. C. circuit 155. Hence, the D. C. circuit 157 will be energized from battery 162 through feeler 153, stationary contact 31, coil spring 81, disc 121, jack screws 123, contactadjustment bushing 121 and its cylindrical extension 124 to lead 171, terminals 185 and 184 of terminal connector box 170, to lamp 166 and back to the battery 162. Hence, the lamp 166 will be energized as an automatic notice to operator that the movable contact 31 is too far in the direction of the feeler 153. It will be noted that due to air gap between feeler 151 and bridging contact 31 the D. C. circuit 155 will not be energized and hence the lamp 165 of that circuit will not light up. When the bridging contact 31 is too far to the left and the lamp 166 is energized, as seen in Figure 8, the operator can adjust the alignment of the mating contacts 26-28-31 by inserting a screw driver in the opening 135 of the contact block 126 and adjust the jack screws 123 until the lamp 166 is de-energized. When both the lamp 166 and 165 are de-energized, the operator will be assured that the bridging contact 31 is in lateral alignment and when the two indicator lamps 166-168 are extinguished the operator will know that the contact member 31 is in transverse alignment. That is, when all the lamps 165 are extinguished the bridging contact 31 will be in proper mating alignment with the stationarycontacts 26-28.

When this condition is achieved by adjustment of jack screws 123, the D. C. circuitry 155, 156, 157, 158 can be removed by disengaging the four clamps 160 and detaching lead 171 from the cylindrical extension 124. The contact assembly 70 is now in proper mating alignment and can be placed in the mechanical rectifier in a manner which will now be described.

The contact mechanism assembly is seen in side view in Figure 6 and in top view in Figure 7.

The D. C. bus bars 20 and 21 extend on both sides and the A. C. bus bars a, 10b, 100 (not shown) are located below the D. C. bus bars. The contact assemblies 70, 71 etc., are held in the contact mechanism assembly in contact with the D. C. bar 20 and 21 and A. C. bar 10a by means of bracket members 180, 181, 190.

As best seen in Figure 6, the end bracket members 181' 131 are held securely against the top surface of the contact block 126 by means of bolt and washer 182-183 which are secured to the support bracket 1 85 at the threaded end 186. The middle bracket 190 is similarly held against the contact block 126 by means of bolt and washer 192-193 which threads with the support flange 195. Coil springs 187 and 197 bias the brackets 180-181 and 190 respectively upward to keep these members from falling into the space occupied by the contact assemblies -71 when they are removed.

Removal of the contact assembly 71 is accomplished by loosening the bolts 182-192 sufliciently to enable the brackets -190 to be rotated free of the contact assembly 71. Since the force of the brackets 180-190 is the only holding and securing means for the contact block, it can readily and easily be removed from the contact mechanism assembly when the brackets 180-190 are rotated out of the Way. The compression springs 187-197 will hold the brackets 180-190 in their up position. After repair, the removed contact assembly 71 or another unit can be replaced in the contact mechanism assembly and secured in position by means of brackets 180-190.

The end support brackets are constructed with a groove or opening 300 between its support legs 301. The openings 300 in support brackets 185 are in alignment with the channels 138 of contact blocks 70 and 71. The middle support bracket is U-shaped with its center opening in alignment with the above mentioned opening 300 and channel 138. Hence, a complete air channel exists from the right hand end, through window or opening 300 in end bracket 185, through channel 138 to area surrounding the contacts 25-30-27, channel 138 on the left on block 71, opening in middle support bracket 195, channel 138 on the right of block 70, area surrounding contacts 23-31-26, channel 138 on the right of block 70 and through the opening 300 in the right support bracket 185. Thus, the operator may observe through window 300, on the left or right of the structure supporting the contact blocks 70-71, the condition of the cooperating contacts when the converter is running. Hence, the operator will have a visual indication of excess sparking at the contacts or undue corrosion or destruction of the silver contacting surfaces.

In summary, my invention relates to a contact assembly unit 70 for a mechanical converter-which is easily adjusted to eliminate bouncing of the co-operating contacts and to ensure proper alignment of the mating contacts, is rapidly and easily installed and removed from the converter, is interchangeable, simple in design and has the advantage of being removable and replaceable.

In the foregoing, I have described my invention only in connection with preferred specific embodiments thereof. Many variations and modifications of the principles of my invention, Within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. A converter providing a unidirectional current comprising a contact assembly, said contact asssembly comprising a bridging contact and a pair of stationary contacts, said bridging contact being a substantially rigid member, biasing means to bias said bridging contact into engagement with said stationary contact, a push rod assembly to etfect contact disengagement during a step length created by a commutating reactor, adjustment means tomodify the etfective length of said push rod, a second adjustment means externally operable to adjust the alignment of said bridging contact with respect to said stationary contact during operation thereof.

2. A contact'assembly comprising a contact block, a bridging contact, two stationary contacts, a compression spring, a contact adjustment bushing, and a disc; said bridging contact secured to one end of said compression spring and said disc secured to the other end thereof to form a spring assembly, said'stationary contacts secured to said contact block, said spring assembly positioned between said stationary contacts and said contact adjustment bushing in said contact block, a plurality of jack screws in threaded engagement with said contact adjustment bushing, adjustment of said jack screws altering the engagement between said bridging contact and said stationary contact.

3. A contact assembly comprising a pair of cooperating contacts, said cooperating contacts being substantially rigid members, biasing means to bias said contacts into contact engaged position, externally operable auxiliary adjustment means connected to alter the alignment of said cooeprating contacts during operation thereof.

4. A contact assembly comprising a pair of cooperating contacts, biasing means to bias said contact into contact engaged position, auxiliary adjustment means connected to alter the alignment of said cooperating contacts, said adjustment means comprising a contact adjustment bushing and jack screws, electrical circuitry to indicate when said cooperating contacts are improperly aligned, adjustment of said jack screws altering the alignment of the mating surface of said cooperating contacts.

5. A converter providing a unidirectional current comprising a contact assembly, said contact assembly having a pair of cooperating contacts biased into contact engaged position, said cooperating contacts being substan tially rigid members, externally operable auxiliary adjustment means to alter the alignment of said cooperating contacts during operation thereof, said contact assembly and said mechanical converter adapted for rapid and easy removal and replacement of said contact assembly from said mechanical converter.

6. In a bridge type contact device for a mechanical rectifier comprising a first and second contact which are normally in high pressure engagement; said first contact comprising a substantially rigid member, said first contact driven by a push rod assembly for oscillatory movement to periodically disengage said second contact; externally operable adjustment means to alter the alignment of said contacts with respect to each other during operation of said first contact into and out of engagement with said second contact.

7. A bridge type contact device for a mechanical rectifier comprising a movable contact and a stationary contact which are normally biased into high pressure contact engagement; said movable contact driven by synchronous means and having oscillatory movement to periodically disengage and engage said stationary contact; a plurality of auxiliary adjusting units to correctly center said movable contact with respect to said stationary contact; said stationary and movable contact and said plurality of adjustment means contained within and forming a single housing unit which can be removably mounted on a mechanical rectifier.

References Cited in the file of this patent UNITED STATES PATENTS 1,5 13,059

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